Uninterruptible power supply

ABSTRACT

A noncontact physical property measurement instrument which easily and accurately measures physical properties of an object using a nondestructive, noncontact sensor. A noncontact physical property measurement instrument  1  is provided with a transmitting section  21  and a receiving section  22 . The transmitting section  21  sends a wave to an object  41  in a medium  100 , and the receiving section  22  receives a wave reflected from the object  41  and the surface of a coating  42 . Both the transmitting section  21  and the receiving section  22  are connected to a gain change correction circuit  13  to form a self-excited oscillating circuit  11  serving as a feedback loop. The gain change correction circuit  13  corrects the gain to the increase side according to a phase difference between the sent wave and the reflected wave, to thereby measure any changes due to a difference in physical properties of the object  41.

TECHNICAL FIELD

[0001] The present invention relates to a physical property measurementinstrument which measures physical properties of an objectnondestructively and without directly contacting the object.

BACKGROUND ART

[0002] As an instrument capable of ascertaining the physical propertiesof an object by nondestructive testing, there is, for example, thehardness measurement instrument disclosed in Japanese Patent Laid-OpenPublication No. Hei 9-145691by the present inventor. This hardnessmeasurement instrument oscillates a contact element made to contact thesurface of the object being tests and oscillates the contact element toeasily and accurately measure the hardness of the object being testedaccording to an oscillation frequency of the contact element.

[0003] However, such a hardness measurement instruments has a problemthat measurement is not possible when the contact element cannot be madeto contact the surface of the test object because, for example, theobject is covered with a material. In such situations, the conventionaldevices cannot measure the hardness or physical properties of the targetobject.

[0004] Even when the object is exposed, with a conventional device it isdifficult to measure the hardness of the object when the contact elementcould not be contacted to the object under test because, for example,the target object is floating in water.

DISCLOSURE OF THE INVENTION

[0005] The noncontact physical property measurement instrument accordingto the present invention comprises a transmitting section which sends awave to a test object in a medium; a receiving section which receives awave reflected by the object; a self-excited oscillating circuit whichconnects the transmitting section and the receiving section to performfeedback oscillation; and a physical property measurement section whichmeasures physical properties of the object according to an oscillationfrequency of the self-excited oscillating circuit. Thus, differences inphysical properties (e.g., hardness) of the object can be measured fromthe oscillation frequency of the self-excited oscillating circuitwithout directly contacting the contact element to the object to betested. Therefore, even if the surface of the object is coated or it isotherwise not possible or difficult to directly contact the object, thephysical properties of object can still be easily and accuratelymeasured.

[0006] According to the present invention, the self-excited oscillatingcircuit may be provided with a gain change correction circuit which hasa center frequency different from the center frequency of theself-excited oscillating circuit and increases gain in response to achange in frequency. When this is done, the sensibility to the gainchange due to the change in frequency can be enhanced, so that thephysical properties of an object to be tested can be measured moreaccurately.

[0007] According to the present invention, there may also be provided astorage storage section in which is prestored data on an interrelationbetween physical properties and the oscillation frequency of theself-excited oscillating circuit. Provision of such a storage sectionenables faster measurement of physical properties based on the value ofoscillation frequency, without sacrificing accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a schematic structure diagram of a noncontact physicalproperty measurement instrument according to an embodiment of thepresent invention;

[0009]FIG. 2 is a circuitry diagram showing an example of a gain changecorrection circuit according to the embodiment of the present invention;

[0010]FIG. 3 is a frequency-gain-phase change characteristic curve chartshowing a total frequency characteristic having combined respectivefrequency characteristics of a self-excited oscillating circuit and again change correction circuit according to the embodiment of thepresent invention;

[0011]FIG. 4 is a frequency-gain-phase change characteristic curve chartshowing respective frequency characteristics of the self-excitedoscillating circuit and the gain change correction circuit according tothe embodiment of the present invention;

[0012]FIG. 5 is a diagram showing an example of calibrated results ofphysical properties measured by the noncontact physical propertymeasurement instrument according to the embodiment of the presentinvention; and

[0013]FIG. 6 is a diagram showing an example of measured results of achange in oscillation frequency of the noncontact physical propertymeasurement instrument according to the embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Embodiments of the present invention will be described withreference to the drawings. FIG. 1 is a schematic structure diagram of anoncontact physical property measurement instrument, and FIG. 2 is acircuitry diagram of a gain change correction circuit of the noncontactphysical property measurement instrument.

[0015] System Configuration of Noncontact Physical Property MeasurementInstrument

[0016] First, the system configuration of a noncontact physical propertymeasurement instrument 1 according to a first embodiment will bedescribed. This noncontact physical property measurement instrument 1 isprovided with a control unit 10 and a sensor unit 20 and measuresphysical properties (e.g., hardness) of an object 41 included in anobject-containing material 40 in a medium 100 (e.g.,water). Theobject-containing material 40 shown as an example in FIG. 1 is comprisedof the object 41, which is formed of a first object 41 a (aluminum rod)and a second object 41 b (copper rod) which are mutually joined, and acoating 42 (silicon) which covers the exterior of the object 41.

[0017] The sensor unit 20 includes a transmitting section 21 and areceiving section 22. The transmitting section 21 (e.g., an ultrasonicoscillator) converts an electric signal from a gain change correctioncircuit 13 into a wave (e.g., an ultrasonic pulsed wave) and transmitsthe wave to the object-containing material 40 in the medium 100. Thereceiving section 22 (e.g., a detection element) receives a component ofthe wave transmitted from the transmitting section 21 reflected by theobject-containing material 40 and converts the reflected wave into anelectrical signal. This electrical signal is returned to the gain changecorrection circuit 13.

[0018] An amplification circuit 12 is disposed between the gain changecorrection circuit 13 and the transmitting section 21 or the receivingsection 22. In the configuration of this embodiment, the amplificationcircuit 12 is disposed between the receiving section 22 and the gainchange correction circuit 13 and amplifies the electric signal which wasconverted from the wave received by the receiving section 22. Theamplified electric signal is input to the gain change correction circuit13.

[0019] These gain change correction circuit 13, transmitting section 21,receiving section 22, and amplification circuit 12 are componentelements of a self-excited oscillating circuit 11 serving as a feedbackloop.

[0020] The gain change correction circuit 13 which is disposed withinthe control unit 10 has a function to adjust gain (e.g., to increase thegain in response to the increase of the frequency) in response tochanges in frequency, a phase transfer function to adjust to zero an I/Ocombined phase difference between an input phase and an output phase ofthe self-excited oscillating circuit 11 to promote feedback oscillation,and a function to adjust the frequency to make the I/O combined phasedifference zero and to increase a gain change in response to changes inthe frequency (e.g., to increase the gain change in response to anincrease in frequency).

[0021] As the gain change correction circuit 13, for example, a filtercircuit having a frequency-gain characteristic such that the gainincreases in response to the change in the frequency is used. FIG. 2 isa circuit diagram showing an example of the filter circuit used as thegain change correction circuit 13. This filter circuit has resistorsR11, R12, R13, R14, capacitors C11, C12, C13, C14, and an amplificationcircuit AMP. In this example, the resistor R11 is set to 10 KΩ, theresistor R12 is set to 220Ω, the resistor R13 is set to 420 KΩ, and theresistor R14 is set to 2.2 KΩ. Power (12V) is supplied from apower-supply terminal V11 to the amplification circuit AMP and a voltage(−12V) is applied to a standard power-supply terminal V12. In thedrawing, reference symbol Vin indicates a signal input terminal andreference symbol Vout indicates a signal output terminal. This filtercircuit has the characteristics of a band pass filter circuit. The inputterminal Vin of the gain change correction circuit 13 is connected tothe output terminal of the amplification circuit 12, and the outputterminal Vout is connected to the input terminal of the transmittingsection 21.

[0022] Other than the above-described gain change correction circuit 13and amplification circuit 12, the control unit 10 also has a frequencymeasurement section 31 which measures, for example, an oscillationfrequency of the self-excited oscillating circuit 11 as a frequency ofthe reflected wave, a physical property measurement section 32 whichmeasures physical properties, e.g, hardness, according to a frequencymeasured by the frequency measurement section 31, a storage section 33which previously stores an interrelation between the frequency and thephysical properties, an input section 34 which enters instruction inputto the control unit 10, and a display section 35 which shows measuredfrequency values, physical property values or the like.

[0023] Basic Principle of Self-excited Oscillation

[0024] Next, the basic principle of self-excited oscillation will bedescribed. FIG. 3 is a frequency-gain-phase characteristic curve chartshowing a total frequency characteristic having combined frequencycharacteristics of the self-excited oscillating circuit 11 and the gainchange correction circuit 13. The horizontal axis indicates a frequency,and the vertical axis indicates gain and phase. A frequency-gaincharacteristic curve TG indicates a total frequency characteristiccombining the frequency characteristic of the gain change correctioncircuit 13 and the frequency characteristic of the self-excitedoscillating circuit 11. The frequency-gain characteristic curve TG formsa mountain-shaped curve showing that the gain rises as the frequencyincreases in a band of a low frequency, becomes maximum in a band ofresonance frequency f0, and decreases in a high frequency band.Characteristic curve θ11 is a phase characteristic showing an I/O phasedifference between an input phase and an output phase of theself-excited oscillating circuit 11.

[0025] This self-excited oscillating circuit 11 adjusts to zero the I/Ophase difference of the self-excited oscillating circuit 11 at theresonance frequency f0 indicating a gain maximum value TGP of thefrequency-gain characteristic curve TG. Specifically, in theself-excited oscillating circuit 11, the I/O combined phase differenceθ11, which is a phase difference between a phase (input phase) θ1 of theresonance frequency to be output from the receiving section 22 and aphase (output phase) θ2 after the gain rise output from the gain changecorrection circuit 13 and fed back to the transmitting section 21, isadjusted to zero (θ11=θ1+θ2=0). When the adjustment of the I/O combinedphase difference θ11 results in a phase difference between the inputphase θ1 and the output phase θ2 of the self-excited oscillating circuit11 including the gain change correction circuit 13, feedback is repeateduntil the I/O combined phase difference θ11 becomes zero, andoscillation is performed at the point when the I/O combined phasedifference θ11 becomes zero. As a result, feedback oscillation of theself-excited oscillating circuit 11 is performed more securely, and thefeed back oscillation can be promoted. The I/O combined phase differenceθ11 is adjusted by the gain change correction circuit 13. The gainchange correction circuit 13 can easily realize adjustment of the I/Ocombined phase difference θ11 by adjusting center frequency f2 of thefrequency characteristic.

[0026]FIG. 4 is a frequency-gain-phase characteristic curve chartshowing respective frequency characteristics of the self-excitedoscillating circuit 11 and the gain change correction circuit 13. Thehorizontal axis indicates a frequency, and the vertical axis indicatesgain and phase. A frequency-gain characteristic curve 13G of the gainchange correction circuit 13 forms a mountain-shaped curve showing thatthe gain rises as the frequency increases in a low frequency band,becomes maximum in a band of the center frequency f2, and decreases in aband of a high frequency. A characteristic curve θ13 is a phasecharacteristic showing an I/O phase difference of the gain changecorrection circuit 13. A characteristic curve MG is a frequency-gaincharacteristic curve of the self-excited oscillating circuit 11excepting the gain change correction circuit 13. The frequency-gaincharacteristic curve MG forms substantially the same mountain-shapedcurve as that of the frequency characteristic of the gain changecorrection circuit 13, although the center frequency f1, the frequencyband, and the gain maximum value are different.

[0027] In this embodiment, as respectively indicated by thefrequency-gain characteristic curves MG and 13G, the center frequency f1of the self-excited oscillating circuit 11 indicted by a gain maximumvalue P1 and the center frequency f2 indicated by a gain maximum value13GP of the gain change correction circuit 13 are set to frequency bandswhich are deliberately displaced from each other. For example, thecenter frequency f2 of the gain change correction circuit 13 is set to ahigh frequency band against the center frequency f1 of the self-excitedoscillating circuit 11 so that the gain becomes higher as the physicalproperty value of the object 41, e.g., a hardness coefficient, becomeshigher.

[0028] A frequency characteristic or directional characteristic of thereflected wave received by the receiving section 22 varies according tothe physical properties, e.g., hardness, of the object 41, resulting ina change in frequency, gain, phase and amplitude of the electric signalof the self-excited oscillating circuit 11. Specifically, the frequencyof the self-excited oscillating circuit 11 changes (e.g., rises) fromthe center frequency f1 of the self-excited oscillating circuit 11 tothe resonance frequency f11 according to the physical properties, e.g.,hardness, of the object 41. Here, the gain maximum value of thefrequency-gain characteristic curve MG of the self-excited oscillatingcircuit 11 changes from the gain maximum value P1 along thefrequency-gain characteristic curve 13G of the gain change correctioncircuit 13 and to increase from the gain maximum value P1. In otherwords, the frequency-gain characteristic curve MG of the self-excitedoscillating circuit 11 changes to a frequency-gain characteristic curveMG1, and the gain maximum value P1 changes to a gain maximum value P11,and the gain G1 changes to a gain G11, respectively.

[0029] As shown in FIG. 2, because the feedback loop by the self-excitedoscillating circuit 11 contains a resistor and a capacitor, there isalways a phase difference Δθbetween the input phase θ1 and the outputphase θ2 of the self-excited oscillating circuit 11. Here, the gainchange correction circuit 13 has a phase transfer function and adjuststo make the I/O combined phase difference θ11 of the feedback loopincluding the gain change correction circuit 13 zero, so that thefrequency changes further more to reach a stable point of the feedbackoscillation when the I/O combined phase difference θ11 becomes zero, andthe gain also changes. Specifically, the frequency-gain characteristiccurve MG1 of the self-excited oscillating circuit 11 changes to thefrequency-gain characteristic curve MG1, and the resonance frequency f11changes to a resonance frequency f12. In association with the change tothe resonance frequency f12, the gain maximum value P11 changes to again maximum value P12, and the gain G11 changes to gain G12. In otherwords, for a portion corresponding to the phase difference Δθ, thecenter frequency f1 of the self-excited oscillating circuit 11continuously changes, e.g., increases, to the resonance frequency fl2,and the gain G1 continuously changes, e.g., increases, to the gain G12.As a result, frequency variation Δf can be obtained, and gain variationΔG can also be obtained by the self-excited oscillating circuit 11. Atthe point when the frequency variation Δf and the gain variation ΔG ofthe self-excited oscillating circuit 11 are obtained, the I/O combinedphase difference θ11 becomes zero, and the self-excited oscillatingcircuit 11 performs feedback oscillation. In the physical propertymeasurement instrument 1 according to this embodiment, the phasedifference of the reflected wave differs from the irradiated waveaccording to the physical properties, e.g., hardness, of the object 41,so that the frequency variation Δf and the phase difference Δθchangedepending on the physical properties, and such change can be caughtwhere it is expanded. Thus, a detection voltage sufficient for judgingthe physical properties of the object 41 can be obtained.

[0030] Calibration of Noncontact Physical Property MeasurementInstrument

[0031] Next, calibration for measurement of the physical properties bythe noncontact physical property measurement instrument 1 according tothis embodiment will be described. FIG. 5 shows an example ofinterrelation between an oscillation frequency f of the noncontactphysical property measurement instrument 1 calculated by calibration andthe physical property (e.g., hardness S). Here, the calibration isperformed on each measuring condition (e.g., the medium 100 (e.g., type,density, etc.), a temperature at the time of measurement, the coating 42(e.g., its material or thickness) etc.). More specifically, thevariation Δf from the center frequency f1 of the oscillation frequency funder a prescribed condition and the measured physical property value,e.g., hardness value S, are measured a plurality of times on a pluralityof objects 41 (e.g., the first object 41 a, the second object 41 b), andan interrelation between the frequency variation Δf and the hardnessvalue S is calculated according to the measurements as, for example,their linear function. In the example shown in FIG. 5, as a linearfunction S=Q (Δf) satisfying the mean values Δfm (Δfma: the mean valueon the first object 41 a, and Δfmb: the mean value on the second object41 b) of the frequency variation Δf measured on the respective objects41 and their corresponding hardness values S (Sa: the hardness value onthe first object 41 a, and Sb: the hardness value on the second object41 b), their interrelations are obtained. The interrelation Q determinedas described above is then stored in the storage section 33 by, forexample, their coefficients (e.g., q1 and q2 when S=q1 Δf+q2). Duringactual measurement, the stored interrelation Q is read as, for example,the coefficients q1, q2, according to the measuring conditions inputfrom the input section 34, and the physical property, e.g., hardness Sx,is calculated according to the interrelation Q in accordance with themeasured frequency variation Δfx and the measuring condition. Thus, theobject can be estimated from the hardness Sx.

[0032] Measurement of Physical Properties

[0033] Next, measurement of physical properties by the noncontactphysical property measurement instrument 1 according to this embodimentwill be described. FIG. 6 shows the frequency variation Δf obtained whenthe sensor unit 20 scanned in direction Y of FIG. 1 in the configurationconsisting of the noncontact physical property measurement instrument 1and the object-containing material 40 shown in FIG. 1. In FIG. 6, thehorizontal axis indicates the scanning distance Y, and the vertical axisindicates the frequency variation Δf. When measuring, theobject-containing material 40 and the sensor unit 20 are held separatedby a prescribed distance in the X direction of FIG. 1.

[0034] In the structure shown in FIG. 1, acoustic impedance differsbetween a case when a wave is reflected by the surface of the firstobject 41 a and a case when it is reflected by the surface of the secondobject 41 b, so that a phase lag of the reflected wave to thetransmitted wave is different between them. As described above, the gainchange correction circuit 13 changes the oscillation frequency faccording to the phase lag, so that the frequency variation Δf greatlyvaries during the scanning in the direction Y as shown in FIG. 6. Fromthis, it can be known that the object 41 to which a wave is irradiatedhas a portion where the physical properties are different. Next, a meanvalue Δfm1 of frequency changes before the large change and a mean valueΔfm2 of frequency changes after the large change of the frequencyvariation Δf are calculated, and each value is compared with theinterrelation Q according to the measurement conditions stored in thestorage section 33 to calculate or measure the physical property value,e.g., hardness value, of the object 41, and it can be presumed from thephysical property value what material is used for the object 41.

[0035] The present invention is not limited to the above embodiment. Forexample, although in the above embodiment the gain change correctioncircuit 13 is disposed between the amplification circuit 12 and thetransmitting section 21, this circuit could be disposed elsewhere, suchas between the receiving section 22 and the amplification circuit 12.

[0036] Also, the gain change correction circuit 13 may have a propertyto increase the gain when the frequency changes so to increase thevoltage according to the increase in gain. Therefore, in addition to theband pass filter circuit of the above embodiment, for example, alow-pass filter circuit, a high-pass filter circuit, a notch-filtercircuit, a integration circuit, a differentiation circuit, or a peakingamplification circuit can be used as the gain change correction circuit13.

[0037] While in the above embodiment, the center frequency f2 of thegain change correction circuit was set to a frequency band higher thanthe center frequency f1 of the self-excited oscillating circuit 11, thefrequency may be set in a low frequency band.

[0038] Although in the above embodiment the ultrasonic oscillator wasused as the transmitting section, the present invention is not limitedto such a configuration. Other configurations are acceptable, as long asa wave can be sent to the object 41 and the reflected wave can bereceived from the object 41 or the object-containing material 140.Additionally, an electromagnetic wave can also be employed as the waveto be sent. Similarly, the physical property which can be measured bythe present invention is not limited to hardness.

[0039] Industrial Applicability

[0040] As described above, because with the present invention adifference in physical properties of an object can be measured as anoscillation frequency without contacting the contact element to theobject, the physical properties of the object can be measured and moreeasily and more accurately, even when the surface of the object iscoated or when direct contact with the object is otherwise difficult.

1. A noncontact physical property measurement instrument, comprising: atransmitting section which sends a wave to an object in a medium; areceiving section which receives a wave reflected by the object; aself-excited oscillating circuit which connects the transmitting sectionand the receiving section to perform feedback oscillation; and aphysical property measurement section which measures physical propertiesof the object according to an oscillation frequency of the self-excitedoscillating circuit.
 2. The noncontact physical property measurementinstrument according to claim 1, wherein the self-excited oscillatingcircuit is provided with a gain change correction circuit which has acenter frequency different from the center frequency of the self-excitedoscillating circuit and increases the gain when the frequency changes.3. The noncontact physical property measurement instrument according toclaim 1 or 2, further comprising a storage section in which has beenstored data on an interrelation between physical properties and theoscillation frequency of the self-excited oscillating circuit.